PERFORCE change 219713 for review

[Robert Watson]

http://p4web.freebsd.org/@@219713?ac=10

Change 219713 by rwatson at rwatson_svr_ctsrd_mipsbuild on 2012/11/10 00:31:27

	Perform CHERI sandbox checks just before Capsicum sandbox checks,
	rather than earlier in system call handling -- specifically, after
	system call arguments are copied in, and PC updates may have been
	performed.  Otherwise, we repeat the offending system call
	indefinitely, spinning in and out of the kernel.  With this change,
	sandboxed userspace components are now blocked from making system
	calls.

Affected files ...

.. //depot/projects/ctsrd/cheribsd/src/sys/kern/subr_syscall.c#6 edit

Differences ...

==== //depot/projects/ctsrd/cheribsd/src/sys/kern/subr_syscall.c#6 (text+ko) ====

@@ -77,16 +77,6 @@
 	} else
 		traced = 0;
 
-#ifdef CPU_CHERI
-	/*
-	 * Constrain code that can originate system calls if userspace
-	 * sandboxing is available.
-	 */
-	error = cheri_syscall_authorize(td);
-	if (error)
-		goto retval;
-#endif
-
 	error = (p->p_sysent->sv_fetch_syscall_args)(td, sa);
 #ifdef KTRACE
 	if (KTRPOINT(td, KTR_SYSCALL))
@@ -119,6 +109,16 @@
 				goto retval;
 		}
 
+#ifdef CPU_CHERI
+		/*
+		 * Constrain code that can originate system calls if
+		 * userspace sandboxing is available.
+		 */
+		error = cheri_syscall_authorize(td);
+		if (error)
+			goto retval;
+#endif
+
 #ifdef CAPABILITY_MODE
 		/*
 		 * In capability mode, we only allow access to system calls